A variety of methods are used for cellular analysis, including visual and/or automated inspection via light or fluorescent light microscopy. Cellular examinations and analyses of these types are commonly practiced in order to obtain information regarding cell lineage, maturational stage, and cell counts in a sample.
Flow cytometry is a method for identifying and distinguishing between different cell types in a non-homogeneous sample. In the flow cytometer, cells are passed one at a time or nearly one at a time through a sensing region where each cell is irradiated by an energy source. Typically, single wavelength light sources (e.g., lasers, etc.) are used as the energy source and one or more of a variety of sensors record data based on the interaction of the cells with the applied energy. Flow cytometry is commonly used in hematology and has been particularly successful in the diagnosis of blood cancers. In addition to flow cytometry, other analytical methods are used in hematology and in characterizing a population of cells.
Blood samples tend to have a high concentration of cells. Analysis of samples with significantly lower concentrations of cells, whether by flow cytometry or other techniques, is more difficult and therefore less common. In addition, traditional hematology analyzers, which are designed to measure whole blood samples, tend to have limited detection sensitivity for low-end cell concentrations. In some cases, manual examination of samples is the only available method for cellular analysis. Improved methods for analyzing samples with low cell counts are desirable in the fields of medicine, microbiology, and others.